Field of Invention
The invention belongs to a technical field of hydrogen preparation, and relates to a hydrogen preparation system, and particularly relates to a quick-start system for preparing hydrogen via aqueous methanol; meanwhile, the invention further relates to a quick-start method for preparing hydrogen via the aqueous methanol.
Description of Related Arts
Hydrogen energy will become the best energy source in numerous new energy sources in the 21st century. This is because, in the case of combusting coal, gasoline and hydrogen of an identical mass, hydrogen produces the most energy with a combustion product of water instead of ash and exhaust gas and without polluting the environment; whereas the coal and petroleum produce combustion products of carbon dioxide and sulfur dioxide, which may cause a greenhouse effect and acid rain respectively. The coal and oil reserves are limited, while hydrogen mainly exists in water, and the only combustion product is water as well, which may continuously produce hydrogen and would never run out.
Hydrogen is colorless gas. It may release a heat amount of 142 kJ per one gram of hydrogen, which is three times of the heating value of gasoline. Hydrogen is particularly light in weight and is much lighter than the gasoline, natural gas and kerosene, with the result of convenient carrying and transportation, and being used as the most suitable fuel for high-speed flying vehicles of aviation and aerospace and the like. Hydrogen is combustible in oxygen and has a flame temperature up to 2500° C., and is widely used to cut or weld steel materials accordingly.
Hydrogen is widespread in nature. Water is a large warehouse for hydrogen and contains 11% of hydrogen therein. Soil contains about 1.5% of hydrogen; Hydrogen is also comprised in petroleum, coal, natural gas, animals and plants, etc. Hydrogen exists in a form of a compound of water, while water covers about 70% of the earth's surface, leading to very large water storage, in other words, hydrogen is an inexhaustible energy source. If hydrogen can be prepared from water by using an appropriate method, hydrogen would be a relatively inexpensive energy source.
Hydrogen has wide applications and good suitability. It may not only serve as fuel, but also has a function of interconversion among chemical energy, heat energy and mechanical energy as a metal hydride. For example, a hydrogen-reserving metal may have functions of both hydrogen-absorbing exotherm and hydrogen-discharging endotherm, by which heat can be stored for heating and air conditioning at room.
Hydrogen was firstly used in cars as a gas fuel. The united states developed a car by using the hydrogen as the fuel in May, 1976; afterwards, Japan also developed a car by using liquid hydrogen as the fuel; In late 1970s, the Benz Automobile Corporation in the former United Germany carried out experiments on hydrogen, and they drove a car for 110 kilometers by merely using five kilograms of hydrogen.
It is not only clean and easy to start up at low temperature, but also has small corrosion effect on the engine and prolongs the service life of the engine by using hydrogen as the automobile fuel. Since hydrogen and air can be mixed uniformly, it may completely omit carburetors which are generally used in cars, so as to simplify structures of the known vehicles. More interestingly, if only 4% of hydrogen is added into gasoline, which is further used as the fuel of the automobile engine, it may save 40% of gasoline without performing large improvement on the automobile engine.
Hydrogen is easy to become liquid under a certain pressure and temperature, and thus is convenient for transportation by a railway tanker, highway trailer or ship. Liquid hydrogen can be used as fuel for cars and airplanes, as well as rockets and missiles. The Apollo spacecraft flying to the moon in the United States, as well as the Long March launch vehicle for launching an artificial satellite in our country, uses the liquid hydrogen as the fuel.
Besides, it may directly convert the hydrogen energy into electric energy by using a hydrogen-hydrogen fuel battery, which makes the usage of the hydrogen energy more convenient. Currently, such kind of fuel battery has been used in a spacecraft and a submarine with good effects. Naturalness, it is not widely used at present due to the high cost.
Nowadays, the annual production volume of hydrogen in the world is about 36 million tons, the most of which is prepared from petroleum, coal and natural gas, and further consumes the fossil fuel that is inherently critical; while another 4% of hydrogen is prepared by electrolysis of water, which, however, consumes much electric energy and is not cost-effective; as a result, new methods for preparing hydrogen have been actively explored. It may reduce energy consumption and lower cost in chemical production by reforming methanol and water to prepare hydrogen, which is expected to replace the water-electrolytic hydrogen making technology called as an electricity guzzler; the technology utilizes an advanced methanol steam reforming-pressure swing adsorption process to prepare pure hydrogen and a CO2-rich gas mixture, and after a further post-treatment, hydrogen and carbon dioxide can be obtained at the same time.
The methanol and water vapor pass through a catalyst under a certain temperature and pressure condition, and further take place a methanol cracking reaction and a transformation reaction with carbon monoxide in the presence of the catalyst to form hydrogen and carbon dioxide, which is a multi-component and multi-reactions gas-solid catalytic reaction system. The reaction equations are as below:CH3OH→CO+2H2  (1)CH3OH→CO+2H2  (2)CH3OH+H2O→CO2+3H2  (3)
The H2 and CO2, which are generated by the reforming reaction, are separated by a palladium membrane separation, to obtain high-purity hydrogen. The pressure swing adsorption method has high energy consumption and requires for a large equipment, and is not suitable for mini-scale hydrogen preparation.
The existing hydrogen preparation devices usually require for a long time for a cold boot, which is generally above five hours, and some devices even require for one day for a boot. While a warm boot requires to consume a large amount of energy source, to cause a reforming chamber (which generally requires for a temperature higher than 400° C.) or the like in a state of high temperature.
Therefore, the urgent problem need to be solved in the art is that how to achieve a fast cool boot and an assurance of energy saving (and good practicability as well) of the hydrogen preparation device.